I did for a while, but gave up - figured if it's going to wear out, it's going to wear out. Meh - whatcha gonna do?
But I do worry about wearing out my mute key, using it to put it on standby many, many times a day. I'm just not a holster/sleep magnet kinda guy. Maybe it's time for autostandby for me.
I'm with Abe; BlackBerries were designed with trackballs, so I use it. (And my dad was an Industrial Engineer, and drilled it into my head to distrust anything with moving parts!)